So, what exactly is 3D printing, and how does it work? At its core, 3D printing involves a technique called additive manufacturing (“AM”), a process by which materials are fused together, layer—by—layer. AM differs from the familiar “subtractive manufacturing” because the builder does not need to cut down or drill into existing materials to create something.

An AM system often starts with Computer Added Design (“CAD”) software. A designer uses CAD to create a 3D model that can be electronically "sliced" into thin (0.1 mm (+/-)) horizontal cross sections. Descriptions of the slices are then sent to the 3D printer, which then “prints” each horizontal cross-section. One layer fuses on top of the next until the last layer is “printed,” and voila— a 3D replica of a hip implant is yours for use! For those of us who have no idea how to construct a 3D model, preexisting models can be freely downloaded from sites like Thingiverse.com or bought at Shapeways.com.

3D printing can involve a variety of materials. The cheapest printers (just under $1000) use plastic. For example, some AM systems use thermoplastics, which when heated to a given temperature become molten liquid. Through a process called Fused Deposition Modeling (“FDM”), thermoplastics are fed from a spool through a deposition head, which melts the plastic. Sound like a hot glue gun? The 3D printer head deposits a thin horizontal cross-section of plastic onto a platform. The platform then drops down as far as the cross section is tall. For example, if the 3D printer head is depositing a 0.1mm layer of plastic, then the platform will drop .01mm. These steps repeat until all the layers are deposited and the final product is complete. Because a 3D printer is basically using a somewhat more sophisticated form of ink jet printing technology, the “science-fiction” of this futuristic sounding process is becoming more affordable and within reach of hobbyist and ‘do-it-yourselves.’

Micheal Weinberg, It Will Be Awesome if They Don’t Screw It Up: 3D Printing, Intellectual Property, and the Fight Over the Next Great Disruptive Technology, Public Knowledge (Novermber 2010), http://www.publicknowledge.org/print/6316.